A coordinated effort is planned to acquire a greater understanding of the events involved in the development and specification of neural connections, the factors governing their stability, and the trophic, inductive influences exerted by one cell on another. Major projects are: (1) a study of the competitive interaction between foreign and original nerves innervating frog skeletal muscle, leading to repression of some synapses; (2) a study of the physiological properties and morphology of synapses found de novo on frog skeletal muscle; (3) an attempt to demonstrate specificity of synapse formation in cultures of chick spinal cord and skeletal muscle, and immunological manipulation of the system to affect this specificity; (4) a study of the possible neurogenic basis of muscular dystrophy; and (5) determination of the plasticity of respecification of retino-tectal connections in fish, coupled with behavioral analysis of the degree of function restored in cases of "compressed" optic nerve projection.